Increasing safe ironing temperatures of cellulsoe triacetate fibers with swelling agents boiling above 190deg. c.



United States Patent INCREASING SAFE IRONXNG TEMPERATURES OF CELLULOSE TREACETATE FIBERS WITH SWELL- ING AGENTS BGILING ABOVE 190 C.

George Frederick Bull and Ralph James Mann, both of Spondon, near Derby, England, assignors to British Celanese Limited, a corporation of Great Britain No Drawing. Filed Mar. 7, 1957, Ser. No. 644,442

Claims priority, application Great Britain Mar. 29, 1956 14 Claims. (Cl. 8131) This invention relates to the treatment of textile fibers of cellulose acetates of high acetyl value, e.g. acetyl value above 59% calculated as acetic acid. For convenience cellulose acetates having acetyl values above 59% are hereinafter referred to as cellulose triacetates.

The term textile fibers is used as including both continuous filaments of indefinite length and filaments in short lengths such as staple fibers. The textile fibers treated in accordance with the invention may be in any form, for example in the form of woven or knitted fabrics or in the form of intermediate structures used in making fabrics. Such intermediate structures include y'arns made up of continuous filaments or staple fibers or products used for conversion into yarns and comprising continuous filaments or staple fibers more or less loosely held together as in tows, tops, slivers and similar structures.

US. application Ser. No. 400,798, filed December 28, 1953, now Patent No. 2,862,785, December 2, 1958, discloses that textile materials of cellulose triacetates of a normal degree of crystallinity can have their sticking temperatures raised by the action of heat, for example dry heat, or steam or hot Water. The term sticking temperature is defined as the lowest temperature at which a heated iron after standing for 10 seconds on a fabric of the cellulose acetate causes the fabric to stick to its surface;

The sticking temperature is closely related to the tem perature at which the material may be safely ironed without glazing, melting or other undesirable modification taking place. Reference is made in the said specification The safe ironing temperature of textile fibers or fabric thereof is closely related to the sticking temperature and in general for practical purposes is lower, for example about lower. The safe ironing temperature of a fabric may be determined by laying the fabric on a heat-insulating bed of cotton fabric, forexample six layers of cotton madapolam laid over a cotton blanket. A heated iron, for example one of 7 lb. Weight having a surface of sixteen sq. in, is placed on the test specimen for 10 seconds. Trials are made each on a fresh portion of the fabric at a series of temperatures each 10 higher than the preceding one and note is made of the lowest temperature at which the material has undergone glazing. The safe ironing temperature is taken as 10 below this temperature;

thus if glazing was not perceptible at 170 C. but just perceptible at 180 C. the safe ironing temperature may be taken as 170 C.

The simple action of steam or Water at temperatures around 100 C. at atmospheric pressure is too slow to be a commercially useful method of raising the sticking point and safe ironing temperature. The same applied to mere heating of the material at temperatures up to 160 C.

We have now found that this action of heat, and particularly the action of steam on fibers of cellulose triacetate, can be greatly accentuated by the presence in the 3,132,919 Patented May 12, 1964 material of a carboxylic ester of a polyhydric alcohol and especially by the presence of diethylene glycol diacetate. For example, if a woven fabric of fibers of cellulose acetate of 61% tacetyl value is padded with a 300 g.p.l. aqueous solution of diethylene glycol diacetate so as to leave thereon about 55% of its weight of the solution and then steamed for 15 mins. under the conditions ordinarily employed in a textile printing continuous steamer, e.g.

with steam at to 104.5 C. and atmospheric pressure, the sticking temperature can be raised from the neighborhood of 20 C. to around 240 C. The cellulose acetate fibers of the fabric may be those made by dry-spinning a solution of the cellulose acetate in a mixture of methylene chloride and methyl alcohol in the ratio of 93 to 7 by weight. Such a padding and steaming process of raising the safe ironing point and effecting setting of a cellu lose triacetate fabric is very convenient since it can be carried out as a continuous operation on normally available processing equipment; this is not the case with pro cedures involving the use of steam or water under pressure; again, the new process avoids heating of the fabric to high temperatures in air, a procedure which may easily lead to undesirable yellowing of the material.

While diethylene glycol di'acetate' has been found very effective, other carboxylic esters, especially fatty acid esters, of polyhydric alcohols, particularly of polyhydric alcohols containing up to four carbon atoms, may be employed, for example other lower fatty acid (C to C esters of glycol, propylene glycol, diethylene glycol, or glycerol, e.g. diethylene glycol monoaceta-te, glycerol diacetate, glycerol triacetate, and glycol monoacetate. Again alkylethers, especially C -C alkylethers, of the polyhydric alcohols may be employed, for example monoalkyl (C -C ethers, e.-g. of glycol, glycerol, or diethylene glycol; specific examples are diethylene glycol monoethylether and diethylene glycol monobutylether. Further, alkylether carboxylic esters of the polyhydric alcohols may be employed, especially those which are C -C alkyl ether C 'C fatty acid esters; examples are diethylene glycol monoethyl-ether-acetate, diethy'leneglycol. mono-.

butylether acetate, glycol monoethylether acetate, and glycol monobutylether acetate. The foregoing terms lower fatty acid (C to C ester, and C 0 fattyacidester mean an ester of a fatty acid, the acid containing from one to four carbon atoms. Similarly the terms C -C alkyl ether and monoalkyl (C to C ether. mean an alkyl ether of which the alkyl group contains from oneto four carbon atoms. As will be appreciated the term polyhydric alcohol is used as including dihydric alcohols, Advantageously there is used one of the foregoing esters,

ethers or ether-esters of glycol, glycerol or diethylene glycol or other polyhydric alcohol containing up to 4 carbon atoms which either (a) contains a C -C alkylether group and a free hydroxy group, or (b) contains a C -C fatty acid ester group and 'a free hydroxy group, or (c) contains C -C fatty acid ester group and an ether oxygen. Preferably the polyhydric alcohol ester, ether, or ether-ester is one having a boiling point of at least 190 or 200 C. We have further found that the diethylene glycol diacetate or other polyhydric alcohol ester, ether, or ether-ester may be replaced by another swelling agent for the cellulose triacetate, particularly one which is Watermiscible and/or has a boiling point of at least 190 or 200 C. for example benzyl alcohol or acetamide. The polyhydric alcohol derivative or other swelling agent may be one which is miscible to the extent of at least three parts in 100 parts by weight of water at 20 C. and is preferably one which is miscible to the extent of'at least five parts in 100 parts of water at 20 C., indeed it may tate.

It is preferred to impregnate the cellulose triacetate material uniformly with the ester or other swelling agent and then subject the material to heat and particularly to the action of steam. The proportion of the polyhydric alcohol derivative or other swelling agent may vary Within wide limits, for example from to 30% based on the weight of the material, but smaller proportions, e.g. down to 5%, or larger proportions, e.g. up to 50 or 60% may be used. The material maybe impregnated directly with the ester or other swelling agent, e.g. by padding, but it is preferred to impregnate the material with an aqueous liquid containing the ester or other swelling agent, say up to 40% or even up to 50% or 60%. This IS likewise conveniently done by padding. For instance a padding liquor may consist of a -40% or 20 60% aqueous solution of diethylene glycol diacetate and the padding device adjusted so that the material retains an amount of liquid containing the desired proportion of diethylene glycol diacetate. The concentration of the polyhydric alcohol derivative or other swelling agent in the impregnation liquid should not of course be such that the liquid dissolves or otherwise damages the material. In the case of using triacetin or other swelling agent which is not miscible with Water in the proportion employed, an addition of a suitable water-miscible liquid may be made in order to render the aqueous liquid homogeneous. The water-miscible added liquid may be readily volatile for example one of boiling point below 100 C., e.g. methyl, ethyl, n-propyl or isopropyl alcohol. Again it may be of relatively low volatility, for example one of boiling point above 150 C., e.g. glycol, glycerol or diethylene glycol. Thus in the case of triacetin a suitable padding liquid may consist of a mixture of water, triacetin and either isopropyl alcohol or diethylene glycol, containing 300 g.p.l. of triacetin and 300 g.p.l. of the isopropyl alcohol or diethylene glycol. In order that the liquid may remain uniformly disposed on the padded material during subsequent manipulation a small proportion of a thickener may be included in the padding liquid, for example l-3% of water-soluble methyl cellulose.

As an alternative to padding, suitably thickened liquids may be applied by an all-over printing operation.

The impregnated material may be subjected to the steaming or other heat treatment directly and without first removing by drying any water, alcohol or other readily volatile liquid present. As already indicated, steaming at atmospheric pressure is effective for the purposes of the invention. It may be effected in conventional steamers such as are used for the steaming of prints on textile maferials. A machine of the Mather and Platt type in which the fabric to be steamed passes through the steamer Whilst supported and forwarded by a series of rollers is very convenient. The duration of the steaming may be from 5 minutes to 15 or minutes or more. However we may use steaming at super-atmospheric pressure for example with steam at 0.3 to -1 atmosphere pressure above atmospheric pressure. Such pressure steaming may be carried out in a pressure steamer such as is often used for steaming prints on textile fabrics.

Simple heat treatment of the material carrying the die-thylenegly'col diacet-ate or other swelling agent may be used in place of a steam treatment. treatments are preferably carried out under conditions which preclude substantial loss by yolatilisation of water or swelling agent or both. A particularly effective method is to immerse the material carrying the swelling agent in a bath of hot liquid which does not dissolve the swelling agent, for example a bath of hot liquid metal. Thus the material, e.-g. a fabric, carrying the swelling agent may be run through a bath of hot mercury or of a lowmelting alloy such as Woods metal. The treatment may be carried out for example in the well known Standfas molten metal machine. By using temperatures of at least and preferably above 100 C., e.g. l20l50 C., the desired effects can be obtained by a relatively short Such simple heat time of passage, for example from a few seconds to a few minutes, e.g. from 10 seconds to 10 minutes depending on the temperature. Very good results can in general be obtained with times of passage of one to six minutes. Indeed, the raising of the safe ironing point of cellulose triacetate fibers can be efiected by the action of the swelling agent, particularly diethylene glycol diacetate or dior rtri-acetin, at still lower temperatures.

By way of example a woven fabric of continuous filament yarns of cellulose acetate of acetyl value about 61% is padded with a 300 grams per liter aqueous solution of diethylene glycol diacetate on -a padding mangle so as to leave on thefabric about 60% of the solution based on the dry weight of the material. The padded material is then without drying run through a bath of Woods metal at a temperature of -l20 C. the time of contact of fabric and metal being 5 minutes. The material is then well washed in water at 60 C. and dried. The safe ironing temperature is thus raised from about C. to 220 C. or more. A similar result is obtained if the temperature of the molten metal is 145 C. The yarns of the fabric may be those made by dry spinning a solution of the cellulose acetate in a mixture of methylene chloride and methyl alcohol in the ratio of 93 to 7 by weight.

Similar results are obtained by replacing the diet-hylene glycol diacetate solution by an aqueous solution containing per liter 300 grams of glycerol triacetate and either 300 grams of isopropyl alcohol or 300' grams of diethylene glycol.

Subsequent to the steam or other heat treatment, the material may be washed to remove remaining ester or other swelling agent and then dyed or otherwise finished as desired. The treatment indeed appears to facilitate the subsequent dyeing of the material, for example with disperse dyes from conventional aqueous baths. If desired, the treated material may be dyed directly without intermediate washing, use being made of the ester or other swelling agent on the material to facilitate dyeing as described in co-pending application Serial No. 647,488, filed March 21, :1957, now abandoned, of H. C. Olpin and J. A. Bright. If the material is freed from the diethyleneglycol diacetate or other swelling agent by Washing with water before dyeing it is preferably not dried before dyeing, since otherwise the full beneficial effects of the treatment of the invention on the dyeing properties may not be obtained. As indicated in the aforesaid US. application Ser. No. 400,798 filed December 28, 1953.

Cellulose triacetate fibers as ordinarily obtained have in general a sticking temperature not greater than about 200 C. and a safe ironing temperature below C. The present invention particularly contemplates carrying out the heat and swelling agent treatment of such materials until the sticking point or safe ironing temperature has been increased by at least 10 C. or 20 C.

It will be seen from the foregoing that important aspects of the invention include raising the safe ironing temperature ofcellulose triacetate textile fibers by the combined action of the diethylene-glycol diacetate or other swelling agent water and heat, as when steaming material impregnated with the swelling agent or when running the material through a hot metal bath while impregnated with an aqueous composition containing the swelling agent, and that the swelling agent may be present in restricted proportion relative to the material. It will further be seen that the invention includes raising the safe ironing temperature of cellulose triacetate fibers by subjecting them to the action of heat while they carry a restricted proportion of the diethylene glycol diacetate or other swelling agent.

The textile fibers of cellulose triacetates treated in accordance with the invention may be any of those referred to in the above mentioned U.S. application Ser. No. 400,798 filed December 28, 1953 for treatment in accordance with that specification.

Having described our invention, what we desire to secure by Letters Patent is:

1. The process of raising the safe ironing temperature of fibers of cellulose triacetate of acetyl value over 59% by weight calculated as acetic acid, said fibers having a safe ironing temperature below 190 C., which comprises impregnating the fibers with a quantity of a mixture comprising water and a water-miscible organic compound which is a swelling agent for the cellulose triacetate, the swelling agent having a boiling point of at least 190 C. and the quantity of the mixture being such as contains from 5 to 60 percent of the swelling agent based on the weight of the fibens, and thereafter heating the fibers impregnated with Water and with said swelling agent, to a temperature of 100 to 150 C. until the safe ironing temperature has been raised by at least C., the presence of the swelling agent speeding up the increase in the safe ironing temperature as contrasted with heating in the absence of the swelling agent.

2. The process of raising the safe ironing temperature of fibens of cellulose triacetate of acetyl value over 59% by weight calculated as acetic acid, said fibers having a safe ironing temperature below 190 C., which comprises impregnating the fibers with a quantity of a mixture comprising water and a water-miscible organic compound which is a swelling agent for the cellulose triace tate, the swell-ing agent having a boiling point of at least 190 C. and the quantity of the mixture being such as contains from 5 to 60 percent of the swelling agent based on the weight of the fibers, and thereatter steaming the impregnated material with steam of from atmospheric pressure to one atmosphere above atmospheric pressure for from 5 to 30 minutes, the presence of the swelling agent speeding up the increase in the safe ironing temperature as contrasted with heating in the absence of the swelling agent.

3. Process according to claim 2 wherein the swelling agent is diethylene glycol monoethyl ether acetate.

4. A process according to claim 2 wherein the swelling agent is a C to 0., fatty acid ester of a polyhydric alcohol, which polyhydric alcohol contains from 2 to 4 carbon atoms, the swelling agent is present in the impregnated fibers to the extent of 10 to 30 percent on the weight of the fabric, and steaming is effected at substantially atmospheric pressure.

5. Process according to claim 4, wherein the ester is diethylene glycol diacetate.

6. Process according to claim 5, wherein the fibers are impregnated with a 20% to 60% aqueous solution of the diethylene glycol diacetate.

7. Process according to claim 4, wherein the ester is glycerol diacetate.

8. Process according to claim 4, wherein the ester is glycerol triacetate.

9. The process of raising the safe ironing temperature of a fabric of fibers of cellulose triacetate of acetyl value over 59% by weight calculated as acetic acid, said fabric having a safe ironing temperature below 190 C., which mixture comprising water and a water-miscible organic compound which is a swelling agent for the cellulose triacetate, the swelling agent having a boiling point of at least 190 C. and the quantity of the mixture being such as contains from 5 to percent of the swelling agent based on the weight of the fabric, and thereafter heat ing the impregnated fabric by passage through liquid metal at a temperature of to C., said liquid metal being inert to the fabric and the time of passage being from 10 seconds to 10 minutes, the presence of the swelling agent speeding up the increase in the safe ironing temperature as contrasted with heating in the absence of the swelling agent.

10. A process according to claim 9 wherein the swelling agent is a C to 0., fatty acid ester of a polyhydric alcohol, which polyhydric alcohol contains from 2 to 4 carbon atoms and the swelling agent is present in the impregnated fabric to the extent of 10 to 30 percent based on the weight of the fabric. 7

11. Process according to claim 10 wherein the ester is diethylene glycol diacetate and is in the form of a 20-40% aqueous solution.

12. Process according to claim 10 wherein the ester is glycerol triacetate.

13. Process according to claim 9 wherein the swelling agent is diethylene glycol monoethyl ether acetate and is in the form of a 2040% aqueous solution.

14. Process for raising the safe ironing temperature of a fabric of cellulose itriacetate fibers having a safe ironing temperature below C. and an acetyl value over 59% by weight calculated as acetic acid, which comprises padding the material with a 20-60% aqueous solution of diethylene glycol diacetate so as to leave from 10 %-30% by Weight of diethylene glycol diacetate on the material and thereafter steaming the latter at atmospheric pressure for 5 to 30 minutes, the presence of the diethylene glycol diacetate speeding up the increase in the safe ironing temperature as contrasted with heating in the absence of the diethylene glycol diacetate.

References Cited in the file of this patent UNITED STATES PATENTS 1,826,608 Ellis Oct. 6, 1931 2,020,303 Dreyfus Nov. 12, 1935 2,073,629 Ellis Mar. 16, 1937 2,202,804 Wampner May 28, 1940 2,328,682 Schnegg Sept. 7, 1943 2,347,001 Schnegg Apr. 18, 1944 2,514,410 Olpin July 11, 1950 2,862,785 Finlayson Dec. 2, 1958 FOREIGN PATENTS I 313,072 Great Britain Aug. 28, 1930 OTHER REFERENCES Baker: Journal of the American Chemical Society, April 1942, pages 776-782.

Fortess: American Dyestuii Reporter, Aug. 1, 1955,

comprises impregnating the fabric with a quantity of a 60 pages P524 -P537. 

1. THE PROCESS OF RAISING THE SAFE IRONING TEMPERATURE OF FIBERS OF CELLULOSE TRIACETATE OF ACETYL VALUE OVER 59% BY WEIGHT CALCULATED AS ACETIC ACID, SAID FIBERS HAVING A SAFE IRONING TEMPERATURE BELOW 190*C, WHICH COMPRISES IMPREGNATING THE FIBERS WITH A QUANTITY OF A MIXTURE COMPRISING WATER AND A WATER-MIXCIBLE ORGANIC COMPOUND WHICH IS A SWELLING AGENT FOR THE CELLULOSE TRIACETATE, THE SWELLING AGENT HAVING A BOILING POINT OF AT LEAT 190*C. AND THE QUANTITY OF THE MIXTURE BEING SUCH AS CONTAINS FROM 5 TO 60 PERCENT OF THE SWELLING AGENT BASED ON THE WEIGHT OF THE FIBERS, AND THEREAFTER HEATING THE FIBERS IMPREGNATED WITH WATER AND WITH SAID SWELLING AGENT, TO A TEMPERATUREE OF 100 TO 150*C. UNTIL THE SAFE IRONING TEMPERATURE HAS BEEN RAISED BY AT LEAST 10* C., THE PRESENCE OF THE SWELLING AGENT SPEEDING UP THE INCREASE IN THE SAFE IRONING TEMPERATURE AS CONTRASTED WITH HEATING IN THE ABSENCE OF THE SWELLING AGENT. 